Isolation And Identification Of Main Pathogenic Fungi From Sweet Potato After Harvest And Its Interaction With Roots And Roots

Sweet potato is highly susceptible to microbial infestation during storage.Microorganisms include bacteria and fungi.The most serious damage is fungi.Pathogen infection causes the sweet potato roots to rot and deteriorate,resulting in serious economic losses.When sweet potato is infected by pathogenic bacteria,it will produce toxins in infected tissues,such as sweet potato ketone.Excessive consumption will cause serious harm to the human body.Therefore,it is imperative to control the infestation of sweet potato pathogens.However,there are many kinds of pathogenic bacteria infecting sweet potato,and the biological characteristics of different pathogenic bacteria are different.Therefore,it is necessary to first identify the pathogenic bacteria strain,in order to solve the problem of sweet potato disease.The subject identified four pathogens by observing biomorphology and combining18 S rDNA sequence analysis.The biological characteristics of these four pathogens were studied one by one.At the same time,the GC-MS metabolomics technique was used to study the interaction mechanism between Fusarium and sweet potato roots,and the following conclusions were obtained:The results were as follows.The four pathogens isolated from the root tissue of Linan native rot "Xinxiang" sweet potato were identified as Fusarium oxysporum,Fusarium solani,Lasoodiplodia sp and Ceratocystis fimbriata by 18 S rDNA sequence analysis.The biological characteristics of the pathogens showed that the most suitable medium for the growth of the four pathogens were sweet potato juice-glucose medium.The optimum temperature of Fusarium oxysporum and Fusarium solani was 30 °C.The optimum temperature of Lasoodiplodia sp and Ceratocystis fimbriata was 25 °C.The optimum pH of Fusarium oxysporum and Fusarium solani was pH 10.0,the optimum pH of Lasoodiplodia sp was 6.0,the optimum pH of Ceratocystis fimbriata was 8.0;the most suitable carbon source of Fusarium oxysporum is soluble starch,and the nitrogen source is beef extract and yeast powder.The most suitable carbon and nitrogen sources for Fusarium solani are glucose and sodium nitrate.The mostsuitable carbon and nitrogen sources for Lasoodiplodia sp are the fructose and yeast powder.The most suitable carbon and nitrogen sources for the sweet potato,Chitin,are sucrose and peptone.Inhibition of growth of pathogenic hyphae and spore germination test showed that the inhibition rate of 0.1% food grade thiabendazole solution on the mycelium of two pathogens was 100%;the inhibition rate of 0.08mg/ml LAE solution on Fusarium oxysporum hyphae The inhibition rate of Fusarium solani was 61.30%,the inhibition rate of Fusarium oxysporum was 61.67%,the inhibition rate of Fusarium oxysporum hyphae was 61.67%,and the inhibition rate of Fusarium solani was 42.23%..At the same time,all three antibacterial preservatives inhibit spore germination.GC-MS metabolomics was used to study the interaction mechanism between sweet potato roots and Fusarium solani.From the identified 720 metabolites,a total of18 different substances were screened and characterized,13 of which decreased and 5of which increased.Through qualitative and quantitative changes of differentials,it provides a theoretical basis for crop disease resistance mechanism and provides a new direction for antibacterial and disease resistance.After the disease,the malic acid content of the sweet potato is increased.The sweet potato itself increases the malic acid content in order to resist the infection of the pathogenic bacteria,thereby strengthening the self-resistance and preventing the rapid oxidation browning,which has positive significance for the disease resistance of the plant.